Definitions
The following definitions apply to the subsequent discussion:
"Aged ISO Speed" means an ISO speed value determined after storage of the film at 22.degree. C., 50% RH and a radiation of 35 mR for a period of 6 months after manufacture with 1 week latent imaging keeping. PA0 "Average Slope" means the value obtained by measuring the slope of the line connecting the densities at 1.41 and at 0.81 log H above the ISO speed point on a Status M density plot. PA0 "Composite" means, with respect to slope or density of a characteristic curve, that Status M measurement protocol is used to obtain a characteristic curve for each of the three color records, and the slope or density value is then composited by summing 40% of the red value, 40% of the green value, and 20% of the blue value to yield a composite slope (CS) or density (CD). PA0 "Designated" means information provided in human or non-human readable forms and includes a DX code. The information may be provided anywhere in or on the package including without limitation on the wrapping, container, cassette, film, or co-packaged camera. PA0 "Exposure Index" (EI) means an exposure scale other than ISO speed used to designate the speed of a film. PA0 "Extended Overexposure Latitude" (EOL) means that the slope of each of the three records at 2.45 log H above the ISO speed point is at least 75% of the Average Slope (AS) for that record. PA0 "Slope Ratio (G/B)" means the ratio of the Average Slope of the green record divided by the Average Slope of the blue record. PA0 "ISO speed" means the speed determined in accordance with ANSI PH2.27-1988, corresponding to the log H exposure value at a density of 0.15 above Dmin on a Status M density plot. PA0 "log H.sub.aged " means the log H exposure value corresponding to the Aged ISO speed. PA0 "log H.sub.designated " means the log H exposure value corresponding to the designated speed of the film. PA0 "Overexposure Printing Density" means the density resulting from an 18% gray card that is over-exposed by 4 stops (1.2 log H). A normally exposed gray card is considered to be exposed at 0.81 log H above the ISO speed point (0.15 density above Dmin) for a film whose Aged ISO Speed exactly equals the designated speed. Thus, a four stop overexposed gray card would be exposed at 2.01 log H above the ISO speed point. For films whose actual speed does not equal the designated speed, the log H exposure for a gray card is defined as: EQU log H.sub.gray =log (9.07/H.sub.designated). PA0 4-amino-N,N-diethylaniline hydrochloride, PA0 4-amino-3-methyl-N,N-diethylaniline hydrochloride, PA0 4-amino-3-methyl-N-ethyl-N-(2-methanesulfonamidoethyl)aniline sesquisulfate hydrate, PA0 4-amino-3-methyl-N-ethyl-N-(2-hydroxyethyl)aniline sulfate, PA0 4-amino-3-(2-methanesulfonamidoethyl)-N,N-diethylaniline hydrochloride, and PA0 4-amino-N-ethyl-N-(2-methoxyethyl)-m-toluidine di-p-toluene sulfonic acid.
The 4 over exposure point is 1.2 log H more exposed than this value.
Background
The quality of many photograph images can be improved by using a film that has a high speed, or high sensitivity to light. Such films are able to capture image details under much lower light conditions than the corresponding lower speed films. For instance, an ISO 400 speed film is preferred over an ISO 200 speed film. A 400 speed film nominally requires half the exposure required of a 200 speed film in order to obtain the same details. Often times the image is in motion and thus one cannot control the exposure by simply increasing the exposure time. Thus, one reason to choose a high-speed film is to have increased underexposure latitude.
One approach to providing more speed for the consumer is to design a film whose speed is greater than the speed encoded in the cartridge DX code and/or the speed stated on the film packaging. For instance, one might design a film whose speed measures ISO 500 but encode and market it as an EI 400 speed film. This will provide an extra 0.10 log E of underexposure latitude. However, there is a disadvantage to having a film whose speed is faster than the DX code and/or the stated speed. The increase in film speed will cause all exposures to be increased. This, in turn, will result in an increase in the density of the negative. Increased density results in an increase in printing time, a very undesirable disadvantage. In addition, due to effects of paper reciprocity, and transmission of unwanted wavelengths through the exposing filters, increased printing time can lead to errors in printing color and density. Furthermore, whether an image is initially scanned for processing through an optical or digital printing system, there is an increase in scanning noise with more dense negatives, another very undesirable disadvantage.
For an example of the effects on printing time, an increase in speed of 0.10 log H for a film with a conventional film gamma of 0.63 will result in an increase of 0.063 printing density. Such an increase in printing density is equivalent to an increase of 16% in printing time. This is an unacceptable increase in printing time for photofinishing laboratories. Moreover, the increase in printing time is particularly disadvantageous for negatives that are over-exposed For example, for an ISO 400 speed film, some cameras will produce an exposure that is 1.2 log H (4 stops) overexposed in sunny lighting conditions. These negatives would normally require a lengthy printing time because of their high density. A further 16% increase in the already lengthy printing time is even more undesirable. Recognizing that overexposure is increasingly likely as one moves up the speed scale, the increased overexposure printing problem becomes more and more of a problem as speed is increased. An increase in printing density at the above described exposure point is thus considered to be an undesired consequence of using a film that is more sensitive to light than is indicated by the stated speed.
It is desirable to find a means to reduce the printing density disadvantage that results from providing increased film speed. One solution is to reduce the minimum densities of the negative. However, the minimum density is limited by support density, emulsion fog, retained spectral sensitizer dyes, masking couplers, and filter dyes. In a well-designed film the minimum densities have already been reduced as much as practical.
U.S. Pat. No. 5,223,871 discloses a preloaded camera having a lens with a focal length not more than 23 mm and a film element with a close to linear characteristic curve over a specified exposure range to improve manual printability in a photofinishing laboratory. However, the green and blue color records do not exhibit a desired level of parallelism necessary to maintain the same printing density neutral balance over a wide exposure range.
It is a problem to be solved to provide a high speed photographic film that enables improved underexposure latitude and desirable overexposure printing density.